Autoinjectors are commonly used in the pharmaceutical industry. These devices are used both with drugs to be administered in case of emergency (e.g., epinephrine), and with drugs to be administered on a more frequent basis (e.g., alprostadil, exenatide, and etanercept). Autoinjectors are generally considered to be compact and easy to use, and these fully-automated devices can greatly simplify the administration of drugs which cannot be administered orally.
Although the specific design of each autoinjector may differ, many of the devices employ spring-actuated mechanisms. By pressing a button, a syringe needle is inserted into the patient and the drug is delivered. A syringe within the autoinjector may include a plunger fitted within a cylindrical tube or barrel, along which the plunger may slide to expel liquid. Many autoinjectors contain glass syringes.